Genetic counseling: Chorionic Villus Sampling (CVS)
Chorionic Villus Sampling (CVS) Introduction *Discuss the reason for referral. *Elicit prior knowledge about CVS. *Elicit knowledge about AMA or other indications for session. *Assess concerns and set goals for the session. *Provide overview of topics for counseling session. Client & Partner Information *Discuss why it's important to get pregnancy, personal, and family history. *Go over pregnancy history: **G?P? **LMP? EDC? **Infertility? **Exposures? **Medical complications? **How has the pregnancy been going? *Personal background: **Occupation? **Religion? **Ethnicity? **Chronic illness? **Partner exposure? Elicit Family History *Construct pedigree: **Abnormal # miscarriages, stillbirths, infant deaths? **Previous children with chromosome abnormality, NTD, Down syndrome, birth defects, mental retardation? **Consanguinity? **Other concerns/risk factors? What is AMA? *Woman is age 35 & above at expected date of delivery. *As maternal age increases, risks of birth defects increase. *Women do not make new eggs like males make sperm. *They are born will all the eggs they will have in their life and these eggs mature with age. *There are procedures that can be done to assess the risk, but there are also risks associated with the procedures. *The age of 35 is the "magic" number because this is when the risk of the procedure is justified. *The background risk for major birth defects for women of all ages is 3-5%. Explain Chromosome Abnormalities *Explain cells, chromosome, and DNA *Show karyotypes *Explain nondisjunction *Show abnormal karyotypes (trisomy 13, 18, 21, sex chromosome anomalies) *Give a general description of the clinical features and prognoses. **Trisomy 18 & 13 are most severe with most affected dying before the age of 1 year **Trisomy 21 is more mild; characteristic physical features and mild to moderate MR **Turner and Kleinfelter's syndromes are sex chromosome anomalies. Also usually mild. Quote Risks *Show charts to figure risk of chromosome abnormalities. *Give age-specific risks: **Age at CVS: ____________ **Down syndrome: 1 in _______ ( %) **Any CA: 1 in ________ ( %) Discuss the option of CVS *What is it? **CVS is short for chorionic villus sampling **The chorionic villi are wisps of fetal tissue or finger-like projections that attach the pregnancy sac to the uterine wall **CVS is the technique in which this sample of placental tissue is obtained **The technique has been around for approximately 15 years although methods have changed over time **It is unique because it is used to diagnose certain birth defects in the 1st trimester of pregnancy rather than later in the pregnancy like amniocentesis ***It is usually performed at 10-12 weeks gestation *What can it tell me? **CVS can detect certain abnormalities in the fetus ***General chromosome abnormalities ***Specific genetic disorders that have been previously identified **It can determine the sex of the baby. *What can it NOT tell me? **CVS cannot detect neural tube defects such as spina bifida ***For this reason, it may be useful to measure the amount of AFP in the maternal serum at 15-18 weeks gestation ***Also, follow-up with US at 18-20 weeks is recommended **It cannot detect all birth defects or mental retardation ***For example, congenital heart defects, cleft lip & palate cannot be seen. ***Also the severity of the defect cannot be known from CVS *Exactly what does the procedure involve? **Show figures of CVS **Transcervical CVS: ***Done at 10-12 weeks gestation ***A speculum is inserted and the vagina and cervix are cleaned with betadeine ***Some physicians apply a tenaculum to the lip of the cervix which can be painful ***Using US to guide, a thin tube is guided into the placenta ***Gentle suction is applied to the tube to remove the villi ***This method is easiest to perform when the placenta is posterior and close to the cervix ***A larger sample is taken as compared to transvaginal CVS ***Discomfort is often minimal, perhaps similar to a pap smear ***Post-procedure bleeding occurs in up to 10% of patients **Transabdominal CVS: ***Done at 10 weeks gestation or later ***The abdomen is cleansed with betadeine ***A local anesthetic injection may be given ***Using US to guide, a spinal needed is inserted through the abdomen into the uterine wall and into the placenta ***The needle is moved back and forth several times through the placenta ***Suction is used to remove the villi sample ***This method is easiest when the placenta is anterior or away from the cervix ***This method is better for women with a retroverted uterus ***A smaller sample (pieces of villi) is taken as compared to transcervical CVS ***The procedure is usually more uncomfortable than the transcervical method ***Bleeding after the procedure is rare **CVS takes approximately 5-7 minutes (not including prep time) **The baby's heartbeat is monitored by US **The collected sample is examined under the microscope to confirm that fetal tissue and not maternal tissue was collected **If maternal cells were collected, the CVS will be repeated **The sample is sent to the lab **Results are available in approximately 10 days *What will it feel like? **There may be some discomfort when the needle enters the skin and the uterus or when the catheter enters the cervix and placenta **Some say that they feel pressure during the procedure **You may experience a small amount of bleeding after CVS *What are the risks? **The background rate of pregnancy loss at 10-12 weeks is 2-3% **CVS increases the risk of miscarriage by 1/100 (1%) in women with a normal uterus ***Reinforce that 99% of women will have a healthy baby **CVS increases the risk of miscarriage by 5/100 (5%) in women with a retroverted uterus using transcervical CVS **Some studies indicate an increased risk for limb defects when CVS is done before 10 weeks gestation ***When performed at 10-12 weeks, most recent studies do not report an increased risk because limbs have already formed at this point ***The risk is approximately 1/3000 (0.0003%) **There are special considerations for mothers who are Rh negative. They need to take RhoGam after the CVS procedure **There is a low risk of uterine infection **Exercise or strenuous activity is to be avoided for 24 hours after the procedure **Sexual intercourse, douching, tub baths, or tampon use are to be avoided for 72 hours after CVS procedure **CVS is not recommended for women with the following: ***Cervical polyps, overly curved sampling pathway, active genital herpes (for trans-cer) ***Interceding bowel, placenta too far from abdomen surface (for trans-abd) ***Active vaginal bleeding or bleeding disorder **You should notify your doctor if any of the following occur: ***Fever greater than 100.4 F ***Heavy bleeding or cramping ***Amniotic fluid leakage *Why should I choose CVS? **CVS can be done earlier than amniocentesis (10-12 weeks versus 15-18 weeks) **It may reduce a couples emotional stress if at risk for abnormality **The procedure allows for termination at an earlier age ***This is before the pregnancy is visible ***Also before fetal movement is felt **Allows for treatment of fetus affected with 21-hydroxylase deficiency *Why might I not want to choose CVS? **There is a higher risk for pregnancy loss as compared to amniocentesis ***1% for CVS versus 0.5% for amnio **CVS does not detect NTDs **CVS is less commonly done as compared to amnio **With CVS, there is a greater likelihood of needing further invasive testing due to: ***Laboratory failure ***Insufficient sample ***Maternal cell contamination ****Seen in approximately 1.9% of cases ***Mosaic or ambiguous results ****There are 2 or more cell types that are different genetically ****Seen in 1-2% of CVS cases Offer Resources *Literature, contact info, etc. *March of Dimes website Elicit final questions and concerns Reporting of the Results *If they are having the procedure, discuss how they would like to receive the results **Appointment, phone call, etc. **Who will contact them? *Discuss the options: elective abortion, adoption, etc. Material obtained under GFDL Licence from http://en.wikibooks.org/wiki/Handbook_of_Genetic_Counseling